Presensitized positive working lithographic plate



March 12, 1968 D. N. ADAMS ETAL 3,373,021

PRESENSITIZED POSITIVE WORKING LITHOGRAPHIC PLATE Filed Jan. 29, 1964 vINVEN RS DOLOR N. ADA

DANIEL c. THOMAS BY (9lwllmflnukgg'j) A T TORNEYS United States PatentOfilice 3,373,021 Patented Mar. 12, 1968 3,373,021 PRESENSTTHZEDPOSITIWE WURKENG LITHOGRAlHIQ PLATE Dolor N. Adams, leveland Heights,and Daniel C.

Thomas, Warrensville Heights, @hio, assignors to Harrisdntertype(Iorporation, Cleveland, Ohio, a

corporation of Delaware Filed Jan. 29, 1964, Ser. No. 340-929 16 Claims.(Cl. 96--33) The present invention relates to a planographic or surfaceplate, and more particularly, to a presensitized positive workinglithographic plate having a sensitizer including a reaction product,susceptible to coupling, of a lightsensitive diazo compound and anacidic component. The diazo reactant may be a normally negative workingdiazo compound.

Usually in exposing a sensitized plate, the light-exposed areas areconverted to a water-insoluble, oleophilic material defining theprinting areas. It is therefore necessary to use a negative of theactual pattern desired. Such a plate is accordingly termed anegative-working plate.

It has long been desired to produce commercially a sue cessfulpositive'working surface plate, that is, one in which the image can beformed on the plate by direct exposure to the original subject orthrough a suitable positive transparency of the original subject.

Previously, the usual way of preparing a positive-working surface platehas involved the use of a diazo material which in its unexposed state isoleophilic and waterinsoluble but which upon exposure to light changesinto a water-soluble form. In the use of such a diazo material, exposurethrough a positive transparency, stencil, of the like followed byaqueous development leaves the unexposed diazo on the plate to form theimage or printing areas. However, after such a plate is prepared, theunexposed diazo areas which now define the printing portions of theplate are still susceptible to light exposure. Accordingly, it oftenhappens that after the plate is in use on a press, normal room lightgradually causes the inkcarrying diazo material to decompose therebyending the useful life of the plate, particularly for high quality work.

It is, therefore, a principal object of the invention to provide a novelpositive-working planographic plate.

Another object is to provide a positive-working lithographic plate whichafter exposure and development is no longer sensitive to light in eitherprinting or nonprinting areas.

A further object is to provide a positive-working plate in which theimage or printing areas are formed of a water-insoluble, oleophilic,light-insensitive, coupled reaction product of a light-sensitivecompound and an acidic component.

A still further object is to provide a method of preparing apresensitized positive-working surface plate and resulting productwherein a normally negative working diazo compound is used in formingthe background or non-printing areas of the plate as well as the imageor printing areas of the plate.

Other objects of the invention as the description proceeds.

To the accomplishment of the foregoing and related ends, the inventionconsists of the features hereinafter fully described and particularlypointed out in the claims, the following disclosure describing in detailthe invention, such disclosure illustrating, however, but one or more ofthe various ways in which the invention may be practiced.

The accompanying drawing diagrammatically illustrates five sequentialsteps or stages in the exposure and will become apparent treatment of apositive working plate of the present invention.

In accordance with the present invention, a light-sensh tive diazocompound reacts with a cycloaliphatic polyphosphoric acidic component toform a relatively waterinsoluble reaction product. Although a chiefobjective of the present invention is to provide a positive workingplate, one unusual result is that those light-sensitive normallynegative working diazo compounds are well suited for use in the presentplate. In short, a positive working surface or planographic plate may beprepared in accordance with the present invention, in one form, from apresensitized negative Working surface plate by a simple overcoatingprocess involving the use of a cycloallphatic polyphosphoric acid.

The diazo-acidic component reaction product, although water-insoluble,is still light-sensitive and capable of undergoing a coupling reaction.Upon exposure to light, however, (such as ultra violet light) thedefined reaction product becomes water-attractive rather thanink-attractive, and the ability to couple is destroyed. Coupling of thereaction product when not light exposed, on the other hand, impartsink-attractive properties and destroys the light-sensitivity withoutdestroying the waterinsolubility. It is therefore possible throughexposure of selected parts of the indicated reaction product to achievethe differential ability to attract ink or water as required for alithographic plate and, in this case, in a positive reproduction of thepattern or transparency used. Further, since the coupling step destroysthe light sensitivity in those portions so treated, these portions areprevented from becoming water-attractive and ink-rejecting under theaction of light as when a plate containing the coupled reaction productis in use on a printing press.

Considering the parts of the plate in greater detail, a suitable backingor support member is employed to carry the present light-sensitivesystem. Such a support member for a planographic or surface plate isusually in sheet form and flexible, so that it can readily be mountedaround the cylinder of a printing press.

The support member or base for the present plate may comprise coatedpapers such as are used in the manufacture of direct imaged plates orphoto-sensitive plates. Base sheets of this type may include platesformed of paper or other sheet stock coated with an aliginate, casein,carboxymethyl cellulose, or the like. A paper sheet or plate may also besuitably backed by a resin, or a paper sheet may be impregnated with athermosetting resin such as phenol formaldehyde. Ordinarily, however,the support member is metal-surfaced or entire sheets of metal may beused. Metals such as aluminum, zinc, copper, chromium, tin, magnesium,steel, and the like may be employed. Aluminum and zinc are preferred.

Since contact with metal chemically destroys a lightsensitive diazomaterial, as is known in the art, a protective layer is normallyinserted between the diazo and such a metal-surfaced support member. Theutility of the present plate does not depend on any particular materialbeing used as the sub-layer. The function of the layer is, as indicated,merely to prevent direct contact of the metal with the diazo, andtherefore a host of materials may constitute the interleaved protectivelayer or sublayer. The sub-layer need only adhere well to the metalsurface and be non-reactive with the light-sensitive system (it mayreact with a metal base), the present light-sensitive layer havingitself adhesive properties which anchor the light-sensitive layer eitherto a sub-layer or other support base. In general, the preferredsub-layer as ultimately deposited is a water-insoluble, hydrophilicadhesive material that is non-reactive with the diazo material. Anymaterial that can be used as a sub-layer for normally negative-Workingdiazo surface plates can be used as a sub-layer in the present plate. Asexamples of such materials from which a sub-layer may be formed, thefollowing are listed. Combinations of these materials may also be usedto form the sub-layer. These materials are applied from a dispersion orsolution, after which the liquid is removed as by evaporation.

(1) *Polyacrylic acid, polymethacrylic acid, and watersolublesalts'thereof such as the ammonium, potassium and sodium salts, as wellas the amides such as polyacrylamide, and also the monomer of suchacids, for example, acrylic acid polymerized in situ.

(2) Carboxymethyl cellulose and carboxymethyl hydroxyethyl cellulose.

(3) The aliphatic titanates having aliphatic radicals up to andincluding four carbon atoms, the titanates being subsequently hydrolyzedand polymerized.

(4) Modified urea-formaldehyde and melamine-form aldehyde resins asdisclosed in US. Patents 2,715,619, 2,- 796,362, 2,554,475, and2,559,578.

(5) Modified urea-formaldehyde and melamine-formaldehyde resins treatedwith a water-dispersible member of the class consisting of polycarboxycompounds, combined polyhydroxy polycarboxy compounds, and alkali metalsilicates such as sodium, potassium and lithium silicates, andwater-soluble flue-silicates.

(6) An oxide layer of aluminum as formed by the Bauer-Vogel process.

(7) Silicates such as alkali metal silicates.

For the diazo compound or material, those compounds disclosed in US.Patent 3,030,210 may be used, namely, a water-soluble, high molecularweight, light-sensitive diazo compound tannable by ultra violet light.Such diazo resins are normally considered to be negative-working in thegraphic arts.

A method of preparing a very satisfactory diazo compound that may beused in accordance with the present invention is described in US. Patent2,679,498 and in US. Patent 2,100,063. This compound is a condensationproduct of paraformaldehyde with p-diazo-diphenylamine sulfate.Descriptions of still other diazo compounds which may be used are setforth in the following United States Patents: 2,063,631, 2,667,415,2,692,827, 2,714,066, 2,- 773,779, and 2,778,735.

Additional examples of a water-soluble, high molecular weight,light-sensitive diazo compound tannable by ultra violet light which maybe used include:

The condensation product of p-anilinobenezenediazonium sulfate andformaldehyde p,p-Iminodibenzenediazonium chlorideN-methyl-p-anilinobenzenediazonium chloride2,5-diethoxy-4-lauramidobenzenediazonium chloride N,N-trimethylenebis(p-ethylaminobenzenediazonium chloride) p,p-Iminodibenzenediazoniurnchloride reacted with formaldehydeN-benzyl-N-ethyl-p-aminobenzenediazonium chloride N-(2,6-dichlorobenzyl) -N-ethyl-p-aminobenzenediazonium chloride2,5-diethoxy-4-(p-ethoxyphenoxy) benzenediazonium chloride 4-(p-bromoanilino) -'2,5-dibrornob enzene diazonium chloride p-(2,4,6trichloroanilino) benzenediazonium chloride4-anilino-3-(2,5-diethoxyphenylsulfarnoyl)benzenediazonium chloride2,5-dipropoXy-4-(p-tolylthio) benzenediazonium chloride As descrbed inthe cited US. Patent 3,030,210, the diazo compounds, in general, possessthe following characteristics:

(1) They contain light-sensitive groups contributing primarily to watersolubility, that is, a diazoniurn group(s).

(2) The light-senstive molecule is fairly large, mainly containing atleast two groups of the size of phenyl or substituted phenyl groups.

(3) The molecular fragment left when the light-sensitive group impartingwater solubility has left the molecule tends to be reactive especiallywith molecules similar to itself so that a species ofphotopolymerization results.

Diazo compounds as a class meeting the aforesaid prerequisites are thoseof the following formulae:

wherein R is a phenyl radical such as phenyl, halophenyl, that is,bromophenyl, chlorophenyl or the like, carboXyphenyl, alkylphenyl, thatis, toluyl, ethylphenyl and the like, alkoxyphenyl, that is,methoxyphenyl, ethoxyphenyl and the like, an aralkyl radical such ashenzyl, chlorobenzyl, bromobenzyl and the like, cycloalkyl such ascyclohexyl or acyl, that is, acetyl, lauroyl, benzoyl and the like; Y isO, S, NH or NR R being alkyl, that is, methyl, ethyl, propyl or thelike; Ar is an aromatic radical; X is an anion of an acid and R is iminoor polyalkylene, that is, dimethylene, trimethylene or the like.

The preferred diazo compounds are polymeric condensation products of thedefined group of diazo compounds with carboxyl compounds likeformaldehyde, since such condensation products ordinarily have enhancedoleophilic properties when coupled as herein described.

The acid component with which the diazo compound reacts is acycloaliphatic polyphosphoric acid, preferably of the nature of phyticacid. The structural formula of this acid is Phytic acid, thehexaphosphoric acid ester of inositol, is a relatively strong acidcontaining twelve acidic groups. The reaction of the acid component withthe diazo compounds is not fully understood but is believed to be a 1:1mole ratio addition reaction between the chemically active diazo groupand an acidic hydrogen group of the acid. In any event, it is possibleto use partial salts and/ or partial esters of phytic acid and stillrealize advantages of the present invention. It does not appear to be atall critical as to what other reactants block off or react with certainof the acidic hydrogen groups of the acid, as long as such reactants donot interfere with the desired reaction with the diazo group. Thus, onemay use the calcium, magnesium, sodium, potassium, or ammonium partialsalts of phytic acid. Or one may use an aliphatic (saturated orunsaturated) partial ester of phytic acid. Mixtures of the acid, partialsalts, and partial esters (or any two of the three) may also be used.The extent of the esterification or salt formation also is not criticaland depends in part on the nature of the subst-ituent. As one test, theextent and type of esterification or salt formation is acceptable aslong as the phytic acid component:

(1) Is still water-soluble, and

(2) Has an acid pH.

Many coupling agents may be used to react with a coupling diazo as willbe recognized by the art. As examples, the following may be listed:

Pentanedione Resoncinol Catechol N-phenyl diethanolam-ine N- m-tolyl)dieth anolamine N-(m-chlorophenyl) diethanolamine N-rnethyl anthranilicacid Acetic acet-o-anisidide Aceto acet-p-phenetididel-chloro-resorcinol 2,4-dinitroso resorcinol 2,3,4-trihydroxy diphenylDiresorcyl sulfide Resorcinol monoacetate 4-:acetyl resorcinol1-p-tolyl-3-methyl-5-pyrazolone l-phenyl-3-rnethyl-5-pyrazolone1-(4-sulfo) phenyl-3-methyl-5 pyrazolone 1-(4-sulfo)phenyl-3-carboxy-5-pyrazolone Cyclohexylamine Phenol rn-CresolPhenylhydrazine Acetoacetanilide Ethyl acetoacetate Beta naphthylamineTitanium acetylaceton'ate (other metal chelates, iron,

nickel, magnesium, etc.)

2-hydroxy-3-naphthoyl anilide-(naphthol-AS)2-hydroxy-3-naphthoyl-m-nitro anilide (naphthol AS-2-hydroxy-3naphthoyl-o-toluidide (naphthol AS-D)2-hydroxy-3-naphthoyl-p-chloro anilide (naphthol AS-E) N,N-bis (aceto'acetyl)-o-toluidide-naphthol AS-G 2hydroxy-3-naphthoyl-3-chloro-4,6-dimethoxy anilide (naphthol ASITR) 2hydroxy-3-naphthoyl-5-chloro-o-toluidide AS-TR) 2-hydroxy-3-naphthoyl-oanisidide (naphthol AS-OL) 2-hydroxy-3-naphthoyl-o-phenetidide (naphtholAS-PH) 3 hydroxy 2 benzo carbazoyl-p-methoxy-o-toluidide (naphtholAS-SR) 2-hydroxy-3-carbazoyl-4chloro anilide (naphthol AS (naphthol2-hydroxy-3-naphthoyl-2-naphthalide (naphthol AS-SW) 2 hydroxy 3naphthoyl-Z,S-dimethoxy-4-chloroanilide (naphthol AS-LG)2-hydroxy-3-naphthoyl-l-naphthalide (naphthol AS-BO) 2hydroxy-3-naphthoyl-4-chloro-o-toluidide (naphthol ASLB) Beta oxynaphthoic acid Beta-naphthol 3,5-ditertiary butyl catechol lZ-hydroxy-S-carboxyanilido naphthalene Trihydroxy benzene, (pyrogallolor phloroglucinol) The couplers of the naphthol AS series are especiallyeffective, because they increase the oleophilic nature of the coupledimage areas.

GENERAL EXAMPLE 1 Referring to FIGURE 1, the relative sizes have nosignificance and are for purposes of illustration only. In practice, thelayers are extremely thin. To prepare and use a positive working plateof the invention, the base member should be free of all foreign matterwhich might interfere with the deposition of a layer or layers asdesired. If the base is metal-surfaced, such as an aluminum sheet 10, asub-layer 11 of any of the materials previously mentioned may be appliedfrom a suitable solvent, either aqueous or organic as will be apparentfrom the nature of the material. The solution of the sub-layer materialis applied over the metal surface as by dip coating. A sufficient amountshould be applied to cover completely the metal surface and provide athickness necessary to protect a diazo compound from the aluminum sheet.Usually the sub-layer application is rinsed with water to remove anyexcess and then allowed to dry. Thus, the concentration of a sub-layermaterial in its solvent medium may range from about 0.1 percent to aboutpercent by weight or higher, Instead of dip coating, the solution ordispersion of the sub-layer material, as well as that of thesubsequently applied layers, may be deposited over the plate by rollercoating, whirler coating, wipe-on coating, and the like. Alight-sensitive diazo layer 12 is next applied as from an aqueoussolution which may contain from about 0.5 percent to about 5 percent ormore by 6 weight of the compound. After drying, the plate nowcorresponds to the first stage of FIGURE 1.

A solution of phytic acid, or its partial salts or esters as described,is next applied over the diazo layer or film 12. The solvent may bewater or methyl alcohol or a mixture of either or both of these withethyl or propyl alcohol, provided a sufiicient amount of the water ormethyl alcohol is present to maintain the phytic acid in solution(phytic acid being relatively insoluble in ethyl or propyl alcohol).Preferably, the solvent contains from about 0.2 percent to about 5percent or more by weight of the acid component. Although the phyticacid solution is thus shown as a separate layer 13 (second stage), thereis an almost immediate reaction with the light-sensitive diazo layer 12to form a waterinsoluble light-sensitive layer 14 (third stage). Therate of reaction is such that the reaction product is produced beforeany appreciable amount of the diazo layer is dis solved away. While asolution of phytic acid alone has been used quite satisfactorily, it isdesirable under some circumstances to use one or more of the abovealcohols to reduce or minimize any tendency of the solutions to dissolvethe diazo. In general, loss of diazo is reduced by high concentrationsof the phytic acid, higher proportions of alcohol, and lowertemperatures of application.

After drying, the plate is exposed to a source 15 of ultra violet lightand through a positive transparency or pattern 16. The amount of lightexposure is not critical as long as there is sufficient light todecompose the diazophytic acid reaction product and provide hydrophilic,water attractive areas 14 (third stage) in which the coupling ability isthus destroyed.

The light-exposed layer 14 is now treated with a solu tion of a couplingagent. The solvent employed depends on the nature of the agent and maybe either water or standard organic solvents. The fact that thediazo-phytic acid reaction product is water-insoluble permits the use ofa Water solution for the coupling agent when performing this stepwithout damaging that reaction layer. Since the layer is in fact quitethin, the coupling reaction can take place even though the layer isinsoluble in the watersolution of the coupler. In short, coupling takesplace at the interface and/ or to the extent that there is penetrationof the layer without dissolving action. It should be further noted thatin the present system, the diazo compound is not underlying or dispersedwithin a thick matrix of a water loving polymer, such as gum, which hasbeen the case previously. The present condition affords a much morereproducible light speed.

Where organic solvents, if desired, are used for the coupling agent,such solvent may comprise alcohols, such as methyl and ethyl alcohols;aromatic solvents, such as benzene, toluene, and xylene; or dioxane; andthe like. The agent couples the diazo reaction product only in thenon-light-exposed portions to form ink attractive printing areas 18, thediazo reaction product in the light-exposed areas 17 having lost itscoupling ability (fourth stage). Water soluble couplers such asphloroglucinol and pyrogallic acid have been successfully incorporateddirectly into the phytic acid (or equivalent) overcoat and positiveworking plates made therefrom. These plates are then coupled by treatingthe unexposed areas with a solution of a base which preferably alsoincludes a wet-ting agent.

The plate is now desensitized using desensitizers known in the art. Thedesensitizers which have proved most effective have been those having abasic pH. A basic desensitizer dissolves away any residual couplingagent from the plate. As a modification, the densensitizer may beincorporated directly into the solution of the coupling agent. Afterrinsing the plate, it may be lacquered as at 18a. The plate is thenready for printing directly in light without fear of loss of the imageareas 18 and 18a due to such further light exposure. Both the printingporas'zaeai tions and the non-printing portions formed from thesensitized layer 14 adhere well to the underlying sub-layer or basemember.

SPEClZFIC EXAMPLE 2 cal Companys Diazo Resin No. 4) was roller coatedover a sub-layer and then allowed to dry. If desired, the diazo solutionmay be stabilized by the addition of zinc chloride, for example, about/3 mol of zinc chloride per mol of diazo. The resulting diazo coat wasroller coated with a one percent by weight aqueous solution of phyticacid and then air dried.

The prepared plate was next exposed through a positive transparency for1.5 minutes at 3,000 foot candles and then swabbed for two minutes witha coupling solution having this formulation.

Amount Ingredient Pentanedione cc 1 Triaminoethane grams" 3 Deionizedwater cc 98 The plate was now desensitized to remove any residualcoupling agent, the desensitizer having this formulation.

Ingredient: Amount Polyacrylic acid (25% solution) cc 20 Water cc 175Ammonium molybdate "grams" 2.5 Ammonium phosphate do 2.5

(Adjust pH of solution with 28% ammonium hydroxide to a pH of 8) MethylCellosolve cc 0.5 Triethylene glycol cc 1 N-vinyl-Z-pyrrolidone cc 10 Ifdesired, minute amounts (up to 2 cc.s, for example) of known wettingagents can be incorporated into the desensitizer. Finally, the plate islacquered using, for example, a conventional black lacquer and, ifdesired, the plate may be gummed for storage. Plates prepared asdescribed have been run for 35,000 copies on the press. The backgroundof the plate remained clean throughout the test, and there was no lossof detail in the image areas.

SPECIFIC EXAMPLE 3 An aluminum sheet of sufficiently low gauge to bereadily flexed was cleaned of surface grease and other contaminates bybeing immersed for two minutes in an aqueous solution of trisodiumphosphate maintained at l60 F. Thereafter, the plate was washed for twominutes with tap water and subsequently immersed for another two minuteperiod in a desmutting bath consisting of concentrated nitric acid to70%).

Following another two minute rinse of the plate with tap water, aprotective sub-layer was applied to the working surface. The plate wasfirst immersed for two minutes in a 0.55 percent aqueous solution of awater-soluble melamineformaldehyde condensation resin. The plate wasagain washed with tap water for two minutes. Although the condensationresin is water-soluble, a sufficient quantity remains (possibly due toelectrostatic attraction) for subsequent operations. Next apolyacrylamide, sold under the trade name Cyanamer, and having 70percent carboxyl groups and percent amine groups was applied by dippingthe plate in a 0.01 percent aqueous solution of the polymer for twominutes. After a further rinse in a water bath for two minutes, theplate was dripped for an additional two minutes in a 1.0 percent aqueoussolution of zirconium acetate. The plate was once more Washed for twominutes by tap water and then given a final wash with deionized waterand dried. The foregoing applied an impervious sub-layer over thealumium sheet.

Next, the plate prepared as described was immersed in a 0.5 percentaqueous solution of a condensation product of parafiormaldehyde withp-diazo-diphenylarnine sulfate and then passed between rollers anddried. An alcoholic solution of 0.2 percent phytic acid was next whirlercoated over the diazo coat and dried. The alcohol of such solutionconsisted of 10 percent methyl alcohol and percent ethyl alcohol. Therewas an immediate reaction between the diazo and phytic acid films orcoats.

The plate was next exposed through a positive transparency for 1.5minutes at 3,000 foot-candles. The plate was next washed with thecoupling agent of Example 2, although the following coupling agent couldhave been used as well:

Ingredient: Parts by volume Ethanolamine, 0.5% solution of zirconiumtetra- 2,4-pentadionate in dimethyl 1 Formamide 1 Ethanol 87 A wash withtap water was then carried out over the plate in order to remove most ofthe unused excess coupler. After desensitizing and then inking the platewith known compounds and inks for this purpose, the plate was ready forthe press.

in the foregoing examples, known equivalent materials such as thosedisclosed herein may be substituted for those stated in the example. Thetimes and temperatures and other parameters being adjusted where and ifneeded as easily determined by trial and error. The patents cited hereinare hereby incorporated by reference.

Other forms embodying the features of the invention may be employed,change being made as regards the features herein disclosed, providedthose stated by any of the following claims or the equivalent of suchfeatures be employed.

We therefore particularly point out and distinctly claim as ourinvention:

1. A lithographic plate comprising a support member, and alight-sensitive layer overlying the support member comprising thereaction product of a light-sensitive diazo resin and a cycloaliphaticpolyphosphoric acid.

2. The lithographic plate of claim 1 wherein said cycloaliphaticpolyphosphoric acid is phytic acid.

3. A positive-working lithographic plate comprising a support member,and a light-sensitive layer overlying a surface of the support memberadapted for subsequent exposure and development, said layer comprisingthe reaction product of a light-sensitive diazo resin and a reactantselected from the group consisting of phytic acid, the water-solubleacidic partial esters of phytic acid, and mixtures thereof.

4-. The positive-working lithographic plate of claim 3 wherein saidlight-sensitive diazo resin is tannable by ultra violet light andconsists essentially of a polymeric condensation product of formaldehydewith a water-soluble, high molecular weight, light-sensitive diazocompound.

5. A lithographic plate comprising a support member, and alight-sensitive layer overlying said support member comprising thereaction product of a light-sensitive diazo resin and a cycloaliphaticpolyphosphoric acid, said lightsensitive diazo resin being thecondensation product of a diazo compound and a carboxyl containingcompound.

6. The lithographic plate of claim 3 wherein said diazo compoundconsists essentially of a condensation product of paraformaldehyde witha p-diazo-diphenylamine sulfate.

'7. In a presensitized, positive-working lithographic plate comprising ametal-surfaced support member, a lightsensitive diazocompound-containing layer, and a protective layer interposed between themetal surface and the light-sensitive layer to prevent direct contactbetween the metal and the diazo compound; the improvement characterizedby providing as said light-sensitive layer a lightsensitive reactionproduct of a light-sensitive diazo resin and a reactant selected fromthe group consisting of phytic acid, the water-soluble acidic partialsalts of phytic acid, the Water-soluble acidic partial esters of phyticacid, and mixtures thereof.

8. A presensitized, positive-working lithographic plate comprising analuminum sheet, a water-insoluble hydrophilic cover over said sheetprotecting the sheet from reaction with a diazo compound, and alight-sensitive layer overlying the cover, said layer consistingessentially of a stratum of a light-sensitive diazo resin over saidprotective cover reacted in situ with phytic acid.

9. A method of preparing a presensitized, positive- Working lithographicplate comprising applying to a sup port member non-reactive therevw'th alayer of a lightsensitive diazo resin, applying over the layer a film ofan acidic component, which enables the component to react with the diazoresin in situ to provide a Water-insoluble lithographic light-sensitivelayer, said acidic component being selected from the group consisting ofphytic acid, the Water-soluble acidic partial salts of phytic acid, thewater-soluble acidic partial esters of phytic acid, and mixturesthereof.

10. A method of preparing a diazo-presentitized, positive-workinglithographic plate comprising forming on a metal surfaced support memberadapted to define the backing of the plate a water-insoluble protectivecovering to prevent direct contact between the metal and alightsensitive diazo resin, applying over the protective covering fromsolution a coat of a light-sensitive diazo resin and drying, andapplying over the light-sensitive diazo coat from solution an acidiccomponent selected from the group consisting of phytic acid, theWater-soluble acidic partial salts of phytic acid, the Water-solubleacidic partial esters of phytic acid, and mixtures thereof, saidlight-sensitive diazo resin and acidic component combining to form thesensitized layer of the plate.

'11. A method of preparing a presensitized, positiveworking lithographicplate comprising treating a normally negative-working diazo-sensitizedlithographic plate with an acidic reactant selected from the groupconsisting of phytic acid, the Water-soluble acidic partial salts ofphytic acid, the water-soluble acidic partial esters of phytic acid, andmixtures thereof.

12. A method of preparing a lithographic printing plate comprisingforming on a support member adapted to define the backing of the plate alayer comprising the reaction product of a light-sensitive diazo resinand a cycloaliphatic polyphosphoric acid, said layer being non-reactivewith the support member, exposing selected portions of thelight-sensitive layer to light to convert said portions tonon-ink-attractive areas of the plate, and thereafter treating saidlayer with a coupling agent to convert the non-selected portions toink-attractive areas of the plate.

13. A method of preparing a lithographic printing plate comprisingapplying to a support member non-reactive therewith a layer of alight-sensitive diazo resin, applying over the layer a film of an acidiccomponent, which enables the diazo resin to react with the acidiccomponent in situ to form a water-insoluble lithographic light-sensitivelayer, sa id acidic component being selected from the group consistingof phytic acid, the water-soluble acidic partial salts of phytic acid,the Water-soluble acidic partial of phytic acid, and mixtures thereof,exposing selected portions of the light-sensitive layer to light to formhydropliilic areas adapted to define non-printing areas of the plate,and treating the light-exposed plate with a diazo coupling agent tocouple the diazo-acid component reaction product in the non-selectedportions to form inkattractive areas adapted to define the printingareas of the plate, and then desensitizing the non-printing areas.

14. A method of preparing a positive working printing plate adapted forcontinuous use in light without loss of image areas due to such lightcomprising applying to a metal-surfaced support member adapted to definethe backing of the plate a water-insoluble protective covering toprevent direct contact between the metal and a light-sensitive diazoresin, forming over the protective covering from solution a coat of anormally negative-working light-sensitive diazo resin and drying, andapplying over the light-sensitive diazo coat from solution an acidiccomponent selected from the group consisting of phytic acid, thewater-soluble acidic partial salts of phytic acid, the water-solubleacidic partial esters of phytic acid, and mixtures thereof, whichenables said diazo compound and acidic component to react and to form awater-insoluble light-sensitive coupleable layer, exposing selectedportions of the light-sensitive layer to light to destroy the couplingability of the diazo-acidic component reaction product in such portionsand form hydrophilic areas adapted to define non-printing areas of theplate, treating the light exposed plate with a diazo coupling agent tocouple the diazo-acidic component reaction product in the nonselectedportions to destroy the light-sensitivity thereof and formink-attractive areas adapted to define the printing areas of the plate,desensitizing the non-printing areas, and lacquering the printing areasto intensity the oleophilic nature thereof. 1

15. In an image-bearing lithographic plate adapted for printing,ink-receptive image areas comprising the coupled reaction product of alight-sensitive diazo resin and an acidic component selected from thegroup consisting of phytic acid, the water-soluble acidic partial saltsof phytic acid, the Water-soluble acidic partial esters of phytic acid,and mixtures thereof, and Water-receptive non-image areas comprising thelight-radiated reaction product of a lightsensitive diazo resin and saidacidic component.

16. In an image-bearing lithographic plate adapted for printing,ink-receptive image areas comprising the coupled reaction product of alight-sensitive diazo resin and an acidic component selected from thegroup consisting of phytic acid, the water-soluble acidic partial saltsof phytic acid, the water-soluble acidic partial esters of phytic acid,and mixtures thereof, and Water-receptive non-image areas.

References Cited UNITED STATES PATENTS NORMAN G. TOCHIN, PrimaryExaminer. C. L. BOWERS, Assistant Examiner.

1. A LITHOGRAPHIC PLATE COMPRISING A SUPPORT MEMBER, AND ALIGHT-SENSITIVE LAYER OVERLAYING THE SUPPORT MEMBER COMPRISING THEREACTION PRODUCT OF A LIGHT-SENSITIVE DIAZO RESIN AND A CYCLOALIPHATICPOLYPHOSHORIC ACID.
 12. A METHOD OF PREPARING A LITHOGRAPHIC PRINTINGPLATE COMPRISING FORMING ON A SUPPORT MEMBER ADAPTED TO DEFINE THEBACKING OF THE PLATE A LAYER COMPRISING THE REACTION PRODUCT OF ALIGHT-SENSITIVE DIAZO RESIN AND A CYCLOALIPHATIC POLYPHOSPHORIC ACID,SAID LAYER BEING NON-REACTIVE WITH THE SUPPORT MEMBER, EXPOSING SELECTEDPORTIONS